upgrading factory sub amp and sub?

[musiccitysho]

I just bought a 2 channel mosfet amp and 2 12" subs in an enclosure. My set up right now is the stock premium JBL set up.
Can I just bypass the factory sub amp and stock sub and splice the new amp and subs to the existing output speaker wires in the trunk that run from the radio? I already know I will have to use heavier gauge wire for the power,running it directly to the battery, and a new ground.
Thanks in advance for any suggestions.
Steve

 

[40BelowSummer]

yes you can get the signal from the factory amp, you can get a thing (not sure of model) to convert the signal to low level RCA. you can use the remote wire as well

 

[musiccitysho]

Thanks for the reply, has anyone done it, I searched for some info but for some reason wasnt finding it with my keywords. I checked with a install shop but they wanted $200.00 just to do the install! Im sure I can handle the job myself, it doesnt seem that complex, I just want to get the wiring right and no annoying surprises or buzzing or find out after I started that it really wont work right.

 

[musiccitysho]

One more thing, I was intending to completely disable the factory sub amp and sub, do I still need to get a RCA converter or whatever its called.
Thanks Again for any help!

 

[pathogenic]

Does the amp have speaker level inputs? If not, you need a line-level adapter/line-output converter to go from the speaker level in to an RCA out to plug into the amp. Make sure you get a good one that won't generate any noise.

 

[musiccitysho]

It has 2 different inputs. It has a "high level low impedance MOLEX 4 pin type (male)input and another left/right RCA style input, one is for left and one for right. The amp is the Pyramid PB449X if that helps.http://www.pyramidcaraudio.com/itempage.asp?model=PB449X
Does that mean that I dont need a line output converter?
I apologize in advance for my ignorance on the subject.
Thanks

<small>[ March 01, 2004, 10:05 PM: Message edited by: musiccitysho ]</small>

 

[40BelowSummer]

Are you planning on keeping the stock radio?

<small>[ March 02, 2004, 12:15 AM: Message edited by: guitar333 ]</small>

 

[pathogenic]

First, don't apologize for not knowing. We've all gotta start somewhere.

Basically amplifiers take input through RCA cables. Pretty much all aftermarket head units from the low end to the high end have RCA outputs at the back of the deck. Instead of running speaker wire, an unamplified signal bypasses the deck's internal amplifier and is sent down the RCA cables into the amplifier. The advantage of this is that some sound quality is lost when an already amplified signal is de-amplified and re-amplified by an external amp.

Your factory stereo does not have any such pre-amplified RCA outputs, all it outputs are signals to go to each speaker. Therefore, to install an aftermarket amplifier on the stock stereo system you need a line output converter. What it does is takes a pair (or two) of speaker wires and converts them to RCA so that you can hook up an amp. Some amps such as my Kenwood come with speaker level inputs which eliminates the need for the LOC, but others do not.

If you plan on replacing your factory deck with an aftermarket one, wait until you get the deck and then hook the sub amp right up to the deck's RCA out and save yourself a bit of money on the LOC. If you plan to stick with the factory deck however, you'll need an LOC if your amp does not have speaker level inputs.

Do you anticipate this to be your only upgrade to the stereo? If so, just get the LOC and hook it up. If you plan to add anything else in the future though I highly recommend getting an aftermarket head unit.

Hope this helps. Let me know if you have any other questions.

 

[93medusa]

Don't forget that the JBL system uses electronic crossovers in the amp, if you were to hook up the high level inputs of the amp to the output from the amplifier for the high freq drivers, you would get no bass since the 4 channel amp is highpassed at 170 hz (I believe) The statement that the factory head unit does not put out a preamp signal is also false. The JBL system headunit ONLY puts out a preamp voltage. refer to this post for a wiriing diagram of the JBL system: http://www.shoforum.com/ubb/ultimatebb.php?ubb=get_topic;f=20;t=001256

you could use this diagram to splice into the gray cable that runs from the head unit into the 4ch amp and then supply your sub amp with preamp level inputs. I know that there is just a jumper between the sub amp and the 4ch amp to pass signal along, I don't see a wiring diagram of that anywhere, I would assume that the 4 ch amp just sums up all the chanels and sends a mono signal over to the sub amp. You could possibly splice into that connection to get signal for your new sub amp also.

I'll look at my system tonight to see what you might be able to do. I'll see if i can figure out the pins on the jumper that runs over to the sub amp, that is the best place for you to get signal, it will be crossed over to play 170 hz and below, and should be mono, which is good for subs.

<small>[ March 02, 2004, 02:28 PM: Message edited by: 93medusa ]</small>

 

[musiccitysho]

First off thanks tons for the help and your patience.
I went out and looked at that jumper that runs from the black amp to the silver sub amp and saw 3 wires connected. I assume that one is a common ground and the other 2 are lead wires?, or is one of them a "radio on" signal since I dont see any other wires going to the amp besides a always on power lead and what I assume is a ground that runs from the little black box between the 2 amps (anyone know what that is?).
So can I splice into those 3 in the gray cable for the signal to the new amp. Also since I got conflicting replies about the LOC which is correct concerning the signal from the jumper, is it low level or not?
thanks again

<small>[ March 02, 2004, 07:26 PM: Message edited by: musiccitysho ]</small>

 

[pathogenic]

I said it didn't put out any preamped RCA outs. Or at least I didn't see any RCA connectors when my friend and I installed his amp and sub on his 93 SHO.

I know the speakers are all crossed over but that is to allow biamplification of the lows and highs. We took a signal off both rear speakers and hooked them up to the speaker level inputs on the amplifier. If the rear speakers are high passed it's a lot lower than 170 Hz because the sub amp is low passed at 80 Hz and it hits pretty hard. I'm not making a baseless suggestion, I've tried it and it works. There may be a better way, but I know you can take a signal from the rear speakers.

This in my opinion is the easiest way to do the install. You may be able to get a preamp signal before the amp but if you don't want to cut any factory wiring this is easier. You may also want to look into using a line driver to boost the signal...either preamp off the head unit or after the line output converter the signal will probably be slightly weak.

 

[musiccitysho]

After all the posts and my research all day, not to mention looking at my subs sitting on the livingroom floor not active Im gonna go for it tommorrow. My plan since I have high level Molex inputs and low level RCA inputs is to splice into the jumper that comes off the 4 way amp to the sub amp (since that signal already has had the highs removed) and run jumpers to split it to a 2 way mono input to the new amp. I still dont know if that signal is hi or low level so I'll try the low level RCA inputs first if that doesnt sound right I'll hit up Radio Shack and get a molex plug and use the hi level Molex input. Although I am a little weary since I couldnt find anything on searches about doing it this way!

I'll let you all know how it turns out
Thanks Again
Steve

 

[93medusa]

I was unable to look at my car tonight, but, the jumper cable between amps will be a low level signal. Not a speaker level input, So you would want to get yourself some RCA type connectors. You've got to make sure you get this right, or you could smoke your amp. If you hook up an incorrect wire and it applies an incorrect voltage to the amp, you most likely will fry something, so make sure the wires you use are the right ones. I looked at my 93 helms manual, and unfortunately, they left most of the in depth coverage of the audio system to the EVTM, but from what I can gather, one wire is positive, one wire is negative, and one wire is a mute for the amp. As long as you properly identify the mute wire, you shouldn't have to worry about frying anything.

To clarify, some terms that are often confused in car audio are RCA and Preamp...Preamp refers to the level that is sent from the head unit to the amplifier, it is unmolested and unamplified, RCA is just the common connector used on aftermarket head units. Somehow the term RCA (a type of connector) became synonomous with preamp output. The output from the stock head unit and from the "RCA" preamp outputs from an aftermarket unit are one and the same.

Even if the stock system is not crossed over at 170 hz, you aren't going to be sending subwoofer material to your amplifier if you are using those rear speakers for signal.

"I know the speakers are all crossed over but that is to allow biamplification of the lows and highs."

This statement does not back up your argument at all. The fact that the factory system is bi-amped is exactly the reason it won't work right. Hooking the speaker levels from the rear speakers to the high level inputs on the amp is like hooking up a mid to the tweeter output on the passive crossovers that came with a component set. You may have hooked up your friends subs like this, and you may be getting some sound out of them, but just like the mid hooked up to the tweeter section of a passive crossover, I guarantee it isn't right. This is simple audio principle here, and I'm sure I could get a lot of people to back me up on this. Don't do it ghetto, it will end up being way more work in the end. Trust me, I want you to learn from my past mistakes. That is one of the things that is great about having a forum like this. You don't have to make the mistakes, other people have already made them for you. With that said good luck.

 

[musiccitysho]

Medusa93 thank you much for the time you have given to help me out. I am going to assume the bare wire is the mute though I'm not sure yet of its purpose. I already have some RCA leads to hook it up low level and hopefully if something goes wrong I'll catch it before it frys anything.
Either way its better than paying those hacks at Cartronics in Nashville who quoted me 200.00 for the install and telling me I needed a LOC "thats why it would be so much", even though its already low level....I knew they were BS'ing me.
I'll post tommorrow w/ the results!

 

[93medusa]

Well, when you first think about it, the line output converter makes sense, I read the post a few times thinking that it would work, but then DING DING DING, a little alarm went off in my head. I wouldn't be so quick as to call a local car audio shop a bunch of hacks. Chances are they are much more compentent than say Circuit ****** or Best Suck.

If you have a multimeter, you can test that bare wire in the harness to see when it is hot. You could even probably just use a test light to see when it is on or not. The purpose of it is to keep the sub from popping.

Good luck!

 

[musiccitysho]

Well I got it installed. After much brainstorming about how to pull the signal from the jumper I decided to pull it from the factory sub leads and run a LOC off of them to the new amp, that way I would still be getting the signal w/ the highs removed. It does hit pretty hard and sound good.
The only problem I'm having now is finding a lead to connect the remote to. I tried the dark blue "radio on" one off the 4 way amp's jumper but it cuts powere if more than one lead is connected to it.
So I'm trying to find the right wire to the power antenna mast. From what I can see theres a green one and a red one running along the antenna cable. Anyone know which one would be the right one to splice into to get power when the radio is turned on?

 

[93medusa]

Glad you got it working, but be careful, 85 watts is a lot to be sending into a line output converter, most are only able to take between 25 and 50 watts.

 

[musiccitysho]

Yeh I was also concerned about that but dude assured me that it could handle it. He said thats how he always does it.I hope he's right.
Though I still havent found a suitable lead for the radio on input. I posted that hopefully someone has dealt w/ it before.
THanks again for the help...couldnt have done it w/o it all!

 

[93medusa]

I don't know what there is in the trunk as far as a remote turn on lead, but you can find the one for the radio in the dash pretty easily, just unplug the head unit power harness, and then use either a mulimeter or a test light to find the wire that gets power when the ignition is turned on. I wouldn't tap into the power antenna lead, because the power antenna goes up and down depending on if you are using the radio or not.